1. Field
The disclosed embodiments relate to aircrafts having a windshield. More particularly, the disclosed embodiments relate to an aircraft in which it is possible to replace windshield panes of the glass type with windshield panes of the acrylic type without the aircraft structure having to be modified.
2. Brief Description of Related Developments
In the aeronautical field, it is known to provide the front part of an aircraft, forming the cockpit in which the pilots sit, with several panes in order for the pilots to have an overall view of events outside the aircraft.
Panes are complex structures having a transparent assembly, a peripheral seal, and optionally additional elements such as deicing elements, demisting elements, etc., for example.
In cockpit panes, the front panes forming the windshield must meet particular strength criteria. The transparent assembly generally consists of several structural and non-structural plies of transparent materials which may be:
materials of mineral origin such as glass, quartz, silica, or combinations thereof, and/or
materials of organic origin such as acrylics, polycarbonates or certain resins, or combinations thereof.
The materials and arrangement of the panes are chosen so as to give the panes structural characteristics suitable for the necessary mechanical strength. In particular, a pane must be able to withstand:
variations in pressure and temperature in operation;
impacts of various nature, in particular bird strike, hail; and
scratches and abrasion.
The windshield panes are fastened on a frame, in an opening made in the structure of the aircraft cockpit.
Whatever the type of pane chosen, be it mineral or organic, the pane is pinched and clamped, at a peripheral rim, between a first face of the frame and a window pane retainer.
In the specific case of a pane of the mineral type, that is to say in which the plies ensuring structural strength are made essentially of a mineral material, the window pane retainer is moreover held assembled on a second face of the frame by fastening elements. The deformation of the pane is very slight due to the rigidity of the material of the pane. There is no risk of the pane becoming detached from of the window pane retainer-frame assembly, the pinching of the pane between the frame and the window pane retainer thus being sufficient to hold the windshield in place.
In the specific case of a pane of the organic type, that is to say in which the plies ensuring structural strength are made essentially of an organic material, the pane undergoes greater deformation than panes of the mineral type since the material is much less rigid. Variations in pressure or impacts, inter alia, cause a deformation of the pane which could lead to the pane becoming at least partially detached from the window pane retainer-frame assembly if such a pane is mounted just pinched. To hold the pane in place, it is known in the prior art, in order to avoid this risk, and as illustrated in FIG. 1, to clamp the pane 10 between the first face 121 of the frame 12 and the window pane retainer 13 by way of through-fasteners 15. Coaxial through-holes 128, 104, 138 for the fasteners 15 to pass through are made in the frame, the pane of the organic type and the window pane retainer. Said fasteners are, for example, screw-nuts, preferably having a countersunk head outside the aircraft in order to maintain a surface state taking account of the aerodynamic stresses on the aircraft.
In this case, the frame and the window pane retainer are not directly held assembled together by fastening elements.
The architecture of the windshield frames fitted nowadays on aircraft thus depends on the type of pane chosen.
The choice of pane must be determined very early in the aircraft assembly process since the assembling of the structural components of the front part of the aircraft depends on this. It is, namely, difficult and expensive to envisage replacing a windshield frame since the front part is complex from the structural point of view and comprises numerous systems.